Performance of different fetal weight charts in the prediction of large-for gestational age and associated neonatal morbidity in a multi-ethnic, obese population.

OBJECTIVES: To examine the performance of different fetal growth charts in the prediction of large-for-gestational-age (LGA) and neonatal morbidity at term in a multi-ethnic, obese population.

METHODS: Our retrospective cohort study included 253 non-anomalous, singleton, term pregnancies who underwent serial third trimester ultrasound scans because of maternal BMI 35 and above. We compared the Hadlock, GROW, INTERGROWTH-21st (IG-21), World Health Organisation (WHO), and Fetal Medicine Foundation (FMF) fetal growth reference charts. LGA was defined as a birthweight above the 90th percentile and neonatal morbidity as a composite of NICU admission or 5-minute Apgar score below 7.

RESULTS: 53 (20.9%) infants were born LGA, 27 (10.7%) experienced neonatal morbidity, and 9 (3.6%) were LGA with neonatal morbidity (which we defined as associated morbidity). The Hadlock and GROW charts showed similar performance in predicting LGA with sensitivities of 66.0% for both charts and specificities of 82.5% and 83.5% respectively. The positive likelihood ratios (LR) were 3.77 (2.64-5.40) and 4.00 (2.77-5.78) respectively. IG-21, WHO, and FMF performed similarly and had higher sensitivities of about 85% with specificities between 66 and 72%. The positive LRs were 2.74 (2.16-3.47), 2.50 (2.00-3.12) and 3.03 (2.36-3.89) respectively. All charts had a high sensitivity for predicting morbidity associated with LGA with the positive LRs ranging between 2.35 and 3.61.

CONCLUSIONS: In our obese population all charts performed well at predicting LGA and associated morbidity. However, the choice of fetal reference chart is likely to affect intervention rates. This article is protected by copyright. All rights reserved.